BACKGROUND/AIMS: An ectopic opening of the common bile duct (CBD) into the duodenal bulb is known to cause biliary tract diseases or peptic ulcer. Yet such a case is extremely rare and the clinical significance of this malformation has not yet been clarified. METHODS: Ten patients with an ectopic opening in the duodenal bulb and who were treated at 4 hospitals in the Chungcheong province area were enrolled. Their clinical and radiographic features and the treatment for their combined biliary diseases were retrospectively analysed. RESULTS: The mean age of the ten patients was 73 years (range: 38~84 years, 8 men, 2 women) Eight of 10 patients had clinical signs and symptoms (RUQ abdominal pain: 5, epigastric pain: 3, fever: 3, Melena: 1). The two patients without symptoms were incidentally found to have an ectopic orifice during the evaluation for bile duct dilatation and a regular health check-up, respectively. Nine had duodenal ulcer scars or bulb deformities. Four had active duodenal ulcers and one of them had bleeding from the active duodenal ulcer, which was treated by endoscopic sclerotheraphy. Six of the 10 patients (60%) had biliary tract diseases (CBD stones: 4, cholangitis without CBD stone: 1, IHD stone: 1). Cholangiography was used for evaluation in 9 patients, and it showed dilatation of the CBD or IHD in 7 (78%), a tapered common bile duct at the distal CBD in 7 (78%) and a hook-shaped distal CBD in 8 (89%). Six patients' biliary tract diseases were treated endoscopically (ERCP: 4, PTCS: 2). Duodenal perforation occurred in 1 (10%), who was successfully managed by medical treatment. CONCLUSIONS: An ectopic opening of the CBD in the duodenal bulb is frequently associated with recurrent duodenal ulcer and biliary tract disease. Combined biliary tract disease can be successfully treated endoscopically.